| 摘要 |
PURPOSE:To provide polyester film, the oligomer content of which is low and the surface property of which as stretched and heat-treated film is excellent, by a method wherein unstretched sheet molded by melt-extrusion is heated so as to remove oligomer. CONSTITUTION:Polyester sheet 2 melt-extruded from a die 1 is fed under the state of closely contacting with the surface of a cooling drum 3 rotating at constant speed, cooled and solidified. The polyester sheet cooled on the surface of the cooling drum 3 is heated with a heating roll 5 and a heating device 7, resulting in bleeding out the oligomer existing in the interior of the sheet to the surface of the sheet and removing the oligomer deposited on the surface of the heating roll 5 with a cleaning device 9 so as to keep the surface of the heating roll 5 contacting with the unstretched sheet clean at all times. The cleaning fluid left on the surface of the roll 5 is heated and dried with a heating device 8.
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